I’m testing out Twitter cards on a Tumblr blog, and I’ve added attribution tags both for the site and the author (twitter:site & twitter:creator), which I’ve confirmed by testing the markup directly in the card preview tool, which shows the card with correct attribution. However, when I put the tags on the live site, and put a URL in the testing tool, the cards fail to show the correct site & author, and instead show Tumblr as the source. Examples:

Is this a bug in the preview tool or the expected behavior for Tumblr blogs? If it’s the latter, I’d request that the cards show correct attribution when present and fallback on showing Tumblr as the source when not.